首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   258篇
  免费   3篇
  国内免费   2篇
林业   29篇
农学   2篇
  98篇
综合类   22篇
农作物   1篇
水产渔业   8篇
畜牧兽医   79篇
植物保护   24篇
  2023年   1篇
  2022年   1篇
  2020年   4篇
  2019年   3篇
  2017年   1篇
  2016年   4篇
  2015年   7篇
  2014年   6篇
  2013年   11篇
  2012年   17篇
  2011年   23篇
  2010年   7篇
  2009年   16篇
  2008年   20篇
  2007年   19篇
  2006年   11篇
  2005年   14篇
  2004年   10篇
  2003年   11篇
  2002年   11篇
  2001年   4篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1989年   2篇
  1988年   4篇
  1987年   4篇
  1986年   3篇
  1985年   5篇
  1984年   5篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1977年   3篇
  1974年   2篇
  1972年   1篇
  1970年   6篇
  1967年   2篇
  1964年   1篇
  1939年   1篇
  1932年   2篇
排序方式: 共有263条查询结果,搜索用时 4 毫秒
1.
Field calibrations for a neutron probe and a capacitance sensor (Diviner 2000) for measuring the soil water content of a shrinking–swelling clay soil were substantially different from commonly used default values. Using our field calibrations, the two instruments estimated similar changes in the cumulative water content of a soil profile (0–1 m depth) over one growing season.  相似文献   
2.
The in vitro heparin sensitivity of 6 different commercial activated partial thromboplastin time (APTT) reagents was investigated based on artificial plasma samples prepared by addition of sodium heparin at different activities (0-1.5 IU/ml) to pooled normal canine plasma. Statistical analysis using 2-way analysis of variance was based on APTT ratios (APTT/mean APTT control). Significant differences between the APTT ratios of different APTT reagents (P < 0.00001) were found, which also depended on heparin activity (interaction between the factors; P < 0.00001). For example, mean APTT ratio at 0.7 IU/ml heparin varied between 1.2 and 2.5. The results of this study indicate that recommendations for the control of heparin therapy in dogs by APTT ratio should be reagent specific.  相似文献   
3.
Background: Mammary tumors are the most common neoplasms in female dogs. Malignant tumors may carry a poor prognosis and necessitate surgery. Few data are available on the value of cytologic examination as a diagnostic or prognostic tool for mammary tumors in dogs. Objectives: The objectives of this study were to determine whether cytologic findings in fine‐needle aspirate specimens of canine mammary tumors correlate with histopathologic results and whether the cytologic diagnosis is associated with postoperative outcome. Methods: In this prospective study, fine‐needle aspirate samples were obtained from 50 mammary tumors in 50 dogs. Results of cytologic and histopathologic examination were compared, using the histologic diagnosis as the reference method. Kaplan–Meier log rank analysis was used to evaluate univariate association of the cytologic diagnosis with duration of survival, local control, and metastasis‐free interval. Results: Adequate cytologic samples were obtained in 43/50 (86%) cases. The cytologic diagnosis correlated with the histologic diagnosis for benign and malignant tumors in 40/43 (93%) and 35/43 (81%) cases, respectively. Cytologic examination had a sensitivity of 88% and a specificity of 96% for the diagnosis of malignancy. The cytologic diagnosis had significant univariate association with duration of survival (P=.016), recurrence‐free interval (P=.003), and metastasis‐free interval (P=.014). Conclusions: Cytologic examination of mammary tumors in the dog has satisfactory accuracy, sensitivity, and specificity for the diagnosis of malignancy and is associated with postoperative outcome. Further studies on the diagnostic accuracy of cytology as well as multivariate analysis of its preoperative prognostic value in mammary tumors in the dog are warranted.  相似文献   
4.
5.
Fluorescence in situ hybridization (FISH) has been reported to be an easy and rapid identification method for many human pathogens, but applications for common veterinary pathogens are lacking. Gene probes for FISH of the animal pathogens Streptococcus uberis and Arcanobacterium pyogenes were designed to provide probes for a specific identification of these bacteria from cultures. Specific FISH probes for these species have so far not been published. Both probes recognized all isolates of the target species correctly. With the S. uberis probe SUB 196 no false-positive results were obtained for reference strains as well as for clinical isolates. Probe APYO 183 for A. pyogenes produced false-positive reactions with so far rarely described Arcanobacterium species from animals at standard hybridization conditions. In order to avoid any incorrect classifications of microorganisms as A. pyogenes, two non-labelled competitor probes were designed and successfully evaluated.  相似文献   
6.
7.
8.
Porcine endogenous retroviruses (PERVs) are integrated in the genome of all pig breeds. Since some of them are able to infect human cells, they might represent a risk for xenotransplantation using pig cells or organs. However, the expression and biological role of PERVs in healthy pigs as well as in porcine tumours is largely unknown. Since we and others have recently shown overexpression of a human endogenous retrovirus, HERV-K, in human melanomas, we studied the expression of PERVs in melanomas of selectively bred Munich miniature swine (MMS) Troll. This breeding herd of MMS Troll is characterised by a high prevalence of melanomas, which histologically resemble various types of cutaneous melanomas in humans. Several genetic factors have been defined when studying inheritance of melanomas and melanocytic nevi in MMS Troll. Here we show that the polytropic PERV-A and PERV-B as well as the ecotropic PERV-C are present in the genome of all melanoma bearing MMS Troll investigated. Most interestingly, in the spleen, but not in other organs, recombinant PERV-A/C proviruses were found. PERV expression was found elevated in melanomas when compared to normal skin and viral proteins were expressed in melanomas and pulmonary metastasis-derived melanoma cell cultures. During passaging of these cells in vitro the expression of PERV mRNA and protein increased and virus particles were released as shown by RT activity in the supernatant and by electron microscopy. Genomic RNA of PERV-A, -B and -C were found in pelleted virus particles. Although PERV expression was elevated in melanomas and pulmonary metastasis-derived cell cultures, the function of the virus in tumour development is still unclear.  相似文献   
9.
10.
Airway hyperresponsiveness is a key feature of human asthma and chronic bronchitis and response to the indirectly acting agonist adenosine 5′-monophosphate (AMP) is thought to reflect underlying airway inflammation. To examine whether airway responsiveness testing (ART) with AMP may be used to differentiate healthy cats from those with asthma (FA) and chronic bronchitis (CB), 24 cats (9 FA, 6 CB, 9 controls) underwent ART with AMP at concentrations of 0.1, 1, 10, 100 and 500 mg/mL using barometric whole body plethysmography.The defined endpoint of ART, an increase in enhanced pause (Penh) exceeding 300% of the post-saline value (baseline), was reached in 9/15 patients (7 FA, 2 CB), but in none of the controls. Mean Penh (±SD) at baseline (BL) was 0.49 ± 0.16 for cases, and 0.54 ± 0.16 for controls, and was significantly increased after AMP challenge in clinical cases (2.62 ± 2.20), but not in controls (0.63 ± 0.30, P < 0.05). After separating responder (R) and non-responder (NR) cases, a more pronounced difference after challenge was found (R: 3.96 ± 1.84, NR: 0.6 ± 0.21, P < 0.001). The provocative concentration of the agonist that increased Penh to 300% of BL (PC Penh 300) in R cases was 52.98 ± 48.04 mg/mL AMP. Age had no influence on the responder status or PC Penh 300. It was concluded that AMP challenge may offer a new method for the identification of cats with lower inflammatory airway disease, and possibly for monitoring disease progression or response to therapy.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号